A Boeing aircraft thought to be carrying the four agents released by Moscow earlier Friday has landed at an air force base in Britain, the Press Association (PA) reported, dpa reported.
"It is understood that the Boeing 767-200 carrying the four agents released by Moscow touched down at RAF Brize Norton in Oxfordshire," reported PA.
It said the Foreign Office and the Ministry of Defence refused to comment.
"Civilian aircraft routinely use military airfields under long- standing arrangements set by the MoD," a spokesman said.
The four Russian agents, exchanged for 10 Russian spies flown back from the US to Moscow Friday, are believed to include nuclear researcher Igor Sutyagin and Sergei Skripal, a former Russian colonel convicted of spying for Britain's MI6 intelligence service.